The invention involves a manufacturing process of Christmas tree decorations, especially those with ornaments and racks for fixing the decorations during their processing by vacuum technology.
At present, Christmas tree decorations are manufactured in the way where glass half-products are blown, either manually or by a machine, to required dimensions and shapes, including the process stem. Half-products are then left clear or they can be further coloured and ornamented (fitted with a decor) or they can be silver-plated with consequent colouring and ornamenting operations.
The principle of silver-plating operation is to coat glass half-product internal surfaces with a thin silver layer. For these purposes reduction of silver nitrate complex solution by sodium tartrate, or by other reducing agents, are used. This method has its drawback in using ammonia for transfer of silver nitrate into the complex solution. Apart from the thin layer of silver coating (2 to 4 microns) on the inner surface of the Christmas tree decoration half-product, hazardous chemical compounds that must be disposed of in an environmentally friendly way, also result in this reaction. Moreover, silver nitrate also belongs among hazardous chemicals and its handling is therefore difficult. Operators must wear breathing protection, rubber aprons, rubber boots and gloves to be protected against breathing ammonia vapours or skin contact with silver-plating solutions. Operators also must attend an annual medical inspection.
The above-mentioned problems are eliminated in the manufacturing process of Christmas tree decorations where glass half-products are blown to required dimensions and shapes, including the process stem. The new process principle is based on the idea that the glass half-product is fixed into the rack first and then placed into the metal-coating device where, under vacuum conditions, a thin (1 to 7 microns) layer of metals and/or their alloys is coated on its surface by vacuum plating or vacuum powder coating processes. Metal-coated surfaces created this way may be finished in various colours using clear and colour varnishes either glossy or matt. For vacuum plating or vacuum powder coating processes some of the following metals, or their alloys, can be used: aluminium, copper, iron, nickel, silver, gold, magnesium, tin, chromium, vanadium and zinc.
Before placed into the metal-coating device, the glass half-products for Christmas tree decorations can be suitably masked in the places of intended future ornaments leaving thus, after the coating process and mask removal, transparent uncoated places.
This masking can be achieved by various methods. In one of them the glass half-products for Christmas tree decorations are laid into a cavity of a masking fixture. The cavity exactly follows the glass half-product shape and size in a selected parting plane that can be changed according to selected ornament patterns. A part of the glass half-product is inserted into the cavity and thus protected against metal-coating and only the part projecting out of it is then metal-coated. The parting plane and its shape are made of flexible material providing good adhesion to the glass half, product and secure placement inside Christmas tree decoration is removed from the rack.
Another possibility how to mask desired placed consists of placing at least one removable cover on the glass half-product for Christmas tree decoration. The cover matches the required decor size and shape and closely fits to this surface. Before the coloration process, the cover is removed. The cover may be suitably provided with a sticking surface for a better adhesion to the half-product.
Still another masking method is based on coating the desired places on the surface of glass half-product for Christmas tree decoration with a thin layer of removable substances, like varnishes, that can be easily removed after metal-coating is finished. Coloration processes by clear or colored paints or matt paints may be performed either before or after the removable layer of varnish is taken away.
The above shown masking methods can be arbitrarily combined in a product.
Depending on half product types, various racks are used for fixing of glass half-products for Christmas tree decorations in the metal-coating device. One of possible designs is that the rack consists of a plastic or metal channel containing at least one flexible cover with at least one cavity. This flexible cover is then fixed inside the channel by strutting between the channel side tags. At opposite ends of its lengthwise centre line, the channel is provided with two side pivots to be mounted into journal bearings positioned at opposite sides on the perimeter of working rotating drum of the metal-coating device.
Another possibility of rack design a rack consisting of a bearing metal/plastic rod provided with pivots at its ends to be accommodated in journal bearings located at opposite positions on the perimeter of working rotating drum of the metal-coating device. Crosswise the bearing rod centre-line, sliding/swinging metal/plastic arms are mounted on the rod. The arms are equipped with, at least, one clamp for accommodating and fixing the glass half-product stem. In order to adjust optimum spacing of separate glass half-products for Christmas tree decorations, the arms are provided with locking elements.
One of possible options of the above rack design is represented by an arrangement where the arms are fixed to the bearing rod by one of their ends while the arms are assembled in couples mutually reversed by 90xc2x0. Arms in one couple are positioned one against the other so that one of them is fixed over the bearing rod and the other under it. Clamps for fixing the glass half-product stem are positioned across the longitudinal axis of their relevant arms consisting of two xe2x80x98Vxe2x80x99-shaped jaws that are fitted on their inner sides with saw-tooth notches or roughened surface to accommodate and fix the stem. Active clamp parts of the same arm couples are mutually reversed by 180xc2x0.
Another of possible options of the above rack design is represented by an arrangement where the arms are fixed to the bearing rod by their centres bearing at each their end couples of opposed clamps consisting of two xe2x80x98Vxe2x80x99-shaped jaws that are fitted on their inner sides with saw-tooth notches or roughened surface to accommodate and fix the stem. Active clamp parts of the same arm couples are mutually reversed by 180xc2x0 and clamp couples positioned at the opposite arm ends and clamp couples at the same ends of neighbouring parallel arms are also reversed by 180xc2x0 by its active parts.
If glass half-products for Christmas tree spires are to be accommodated, the rack is designed so that the arms are created by a pre-stressed metal belt fixed at its centre to the bearing rod. The arms are arranged into opposed clamp couples so that each couple arms are closely fitted one to another and the arms are mutually reversed by 90xc2x0. At one arm end, fixings in a form of a conical plug are prepared to accommodate the end of the Christmas tree spire stems. At the opposite clamp couples of the same side, there are fixings shaped as cavities to accommodate the tips of the Christmas tree spires. Counterwise arm couples are mutually reversed by 90xc2x0 so that the conical plugs of one couple are coaxial to the opposite couple cavities.
The above manufacturing process of Christmas tree decorations offers a great advantage in the elimination of conventional silver-plating in silver nitrate solutions and reducing agents, i.e. including ammonia, which means that this is a very suitable, environmentally and health friendly manufacturing -process. Another advantage is that the above process enables to produce completely new products where on surfaces of Christmas tree decorations transparent places are created that may be left either clear or further colour modified or decorated by ornaments.